Most computers use disk drives to store data. A disk drive typically includes one or more disks that the data is stored on, and a slider that are used to write data onto the disks and to read the data from the disks. Conventionally, the slider includes a substrate having an air bearing surface (ABS), a write head for writing data to the disk, a read sensor for reading data from the disk. The air bearing surface (ABS) of the slider provides the aerodynamic properties that enables the slider to “fly” over a disk. The read sensor has a height, which is commonly known as a stripe-height. In order for the slider as well as the read sensor and the write head to function properly, the ABS needs to be very flat and smooth and the read sensors need to have an appropriate stripe-height. Generally, traditional approach that has been effectively used by disk drive manufacturers to achieve the desired smoothness and the desired stripe-height is to employ a lapping plate for grinding and/or polishing the ABS (commonly referred to as the “lapping process”) via a surface profile thereof. Therefore, the quality and characteristic of the surface profile of the lapping plate is critical in lapping the ABS of the slider. Thus disk drive manufacturers are constantly seeking ways to manufacturing a lapping pate of good quality in order to further produce excellent slider.
Till today, disk drive manufacturers have developed a cutting tool to forming the surface profile of the lapping plate. FIGS. 1 to 5 illustrate a conventional cutting tool 10 for the generation of a surface profile of a lapping plate. Referring to FIGS. 1-2, the cutting tool 10 comprises a major body 11 and a cutting body 12. The major body 11 has one end 111 defining a reference surface 111a and the other end 112 forming a cutout (not shown) at a free edge of the other end 112. The cutting body 12 is formed on the cutout of the other end 112 of the major body 11. The cutting body 12 has a first connection surface 121 connecting to one surface of the cutout and a second surface 122 connecting the first connection surface 121 with the other surface of the cutout. Referring to FIGS. 3-4, the first connection surface 121 has an arc-shaped portion 121a at a tip edge thereof. The radius R of the arc-shaped portion 121a is 1 cm and the radian A1 of the arc-shaped portion 121a is 90 degrees. Due to the surface of the lapping plate is usually curve, when the cutting tool 10 acts on the surface of the lapping plate to form a surface profile, the cutting tool 10 performs curvilinear motion along a radial direction D 1 (shown in FIG. 7) of the lapping plate. Generally, the radius R and the radian A1 of the first connection surface 121 of the cutting tool 10 are used to control the surface profile of lapping plate. Returning to FIGS. 1-2, the second connection surface 122 has an inclined portion 122a which is connected to the arc-shaped portion 121a of the first connection surface 121. In addition, the second connection portion further comprises two side portions 122b, 122c which respectively form beside the inclined portion 122a and respectively connect the inclined portion 122a from two sides with portions of the first connection surface 121 other than the arc-shaped portion 121a. Referring to FIG. 5, the arc-shaped portion 121a of the first connection portion 121 forms a first angle A2 with the reference surface 111a, the inclined portion 122a of the second connection surface 122 forms a second angle A3 with the reference surface 111a. The first angle A2 ranges from 6 degrees to 12 degrees and the second angle A3 ranges from 78 degrees to 84 degrees. The first angle A2 is designed for decreasing mechanical vibration in depth direction D2 of the lapping plate, and the second angle A3 is designed for decreasing mechanical vibration in radial direction D1 of the lapping plate.
FIG. 6 illustrates a conventional lapping plate 50. As shown in FIG. 6, the lapping plate 50 comprises a base plate 52 and a tin-bismuth plate 51 formed on the base plate 52. The tin-bismuth plate 51 is made of Sn (Stannum, tin) grains 511 occupying 98% and Bi (bismuth) grains 512 occupying 2%. As the tin-bismuth plate 51 consists of the Sn grains 511 and the Bi grains 512, thus arrangements and combinations of the Sn grains 511 and the Bi grains 512 produce grain boundaries 513 between the Sn grains 511 and the Bi grains 512. FIG. 7 illustrates the cutting body 12 of the cutting tool 10 of FIG. 1 forming surface profile of the lapping plate 50 of FIG. 6. Referring to FIG. 7, when the cutting body 12 of the cutting tool 10 performs curvilinear motion along a desired portion of the tin-bismuth plate 51 of the lapping plate 50 in the radial direction D1, the arc-shaped portion 121a of the first connection surface 121 of the cutting body 12 contacts the desired portion of the tin-bismuth plate 51 and cut the desired portion to form a surface profile. As the desired portion of the tin-bismuth plate 51 contact the cutting body 12 only via the arc-shaped portion 121a, the cutting step of the cutting body 12 makes the arc-shaped portion 121a produce forces on the tin-bismuth plate 51 in the same direction (as shown by arrow F). Resultant force of the forces in the same direction are so large that the Sn grains 511 or Bi grains 512 of the tin-bismuth plate 51 are easily peeled off, which causes to expand the size of grain boundaries 513. When the cutting body 12 continues to perform on the tin-bismuth plate 51 of the lapping plate 50, the size of grain boundaries 513 are likely to grow bigger and bigger to accordingly form Pin-holes in the surface profile of tin-bismuth plate 51, and thereby the lapping plate 50 with Pin-holes surface profile significantly affects the quality of sliders when lapping the sliders using the Pin-holes surface profile of the lapping plate 50.
Hence, it is desired to provide an improved cutting tool for the lapping plate to solve the above-mentioned problems and achieve a good performance.